Field of the Invention
The present invention relates to an image capturing apparatus and a control method thereof.
Description of the Related Art
Recently, large-format image sensors, at sizes of 1″ or more, are being installed even in compact digital cameras. As a result, shooting images at extremely high sensitivities, shooting images at a shallow depth of field to evoke a bokeh effect, and so on, which thus far were only possible with single-lens reflex cameras, are now possible with compact digital cameras as well. Such large-format image sensors have become an essential piece of technology for distinguishing compact digital cameras from the types of cameras installed in smartphones, tablets, and the like.
However, in the case where a large-format image sensor is installed in a compact digital camera, increasing the size of the lens to handle the large-format image sensor will increase the size of the camera as a whole. Thus reducing the size of the lens becomes an issue when installing a large-format image sensor in a compact digital camera. However, if the size of the lens is reduced while ensuring the same performance as a large-format lens, there is a problem in that generally, the angle of incidence of light rays entering the lens (called a “light ray incidence angle” hereinafter) will increase.
Japanese Patent No. 4604307 proposes an image sensor whose image capturing surface has a bent structure as one way of solving this problem. By bending the image capturing surface, this image sensor can ensure that light rays from a subject entering through the lens are orthogonal to the image capturing surface.
Meanwhile, Japanese Patent Laid-Open No. 2012-182194 proposes an image capturing apparatus that employs an image sensor having a bent image capturing surface, in which the curvature of the image capturing surface can be variably controlled from a flat state to a bent state having a predetermined curvature in accordance with a movement amount of an optical lens system. In other words, the curvature of the image sensor can be changed in accordance with a zoom position, an aperture value (F-stop value), or the like of the optical lens system of the image capturing apparatus, which makes it possible to deform the image sensor to curvatures suited to different states in the optical lens system.
A structure in which the image capturing surface is bent and the curvature is variably controlled results in stress in the image sensor substrate itself, and that stress changes in accordance with the curvature of the image capturing surface. In other words, the stress produced when changing the curvature of the image sensor puts stress on the image sensor itself, which is thought to reduce the durability of the image sensor.